Trepidation

Despite his age, seventeen-year-old Ethan Heath has never been on a date, let alone had a boyfriend.

But with his friends pestering him on New Year's Eve, the idea gets stuck in his head.
He caves in and downloads a dating app and quickly meets Trevor Demond, a jock who attends the same school.

It was already too deep in the conversation before Ethan realized his critical mistake setting up his account:

he put himself in as female.